P0157 – O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

Meaning:

When the ECM has determined that there’s a low voltage condition in bank 2 sensor 2, the P0157 happens
The P0157 is triggered when the ECM has determined that there’s a low voltage condition in bank 2 sensor 2

The ECM has determined that there’s a low voltage condition in bank 2 sensor 2; i.e. O2 sensor voltage remained too low for longer than 2 minutes.

Main Symptoms:

  • Check Engine Light comes on
  • Car produces black smoke (visible at tailpipe)
  • Poor fuel economy
  • Engine may fail to start completely
  • If it starts it may run rough and/or stumble

Possible Causes:

  • Mostly a problem related to corrosion, loose terminal or burnt wire in the O2 sensor 2 connector
  • Defective O2 sensor
  • Open or short in wiring to O2 sensor
  • O2 circuit is experiencing high resistance

Diagnostic Steps:

  • Visually inspect all wiring to O2 sensor 2 for loose, open or short connections
  • Use a wiggle test to determine where the voltage drops out
  • Using an OBD2 scanner, check whether sensor 2 of bank 2 is switching properly

Read More: OBD2 Codes List: Meaning, Fixes, and Free Download